I Have Developed An Underarm Rash. The Skin Had Been

I have developed an underarm rash. The skin had been itching for several weeks, but no rash. I switched deodorants but not much luck with the itching. This week, pimple or blister like bumps appeared, with some itching. I used a cortisone cream which helped with the itching, but it kind of aches in the spot where several of the blisters have now blended together, forming a spot about the size of a dime. I stopped using the cortisone cream today and have applied A&D ointment and taken a NSAID for the achy pain.